This invention relates to a vehicle-mounted drive control apparatus for drive-controlling a motor that is supplied with reversible power from a vehicle battery by way of switching devices of a driving circuit and reversibly drives a moving body between a forward limit position and a reverse limit position, and particularly to a vehicle-mounted drive control apparatus with improved handling of overloading of the motor.
Motor drive control units that control the duty ratio of transistors of a bridge circuit constituting a reversible rotation driving circuit controlled by pulse width modulation by a microprocessor are in use in a wide range of applications.
For example in Patent Document 1, ‘Actuator Control Apparatus’, technology is disclosed in which, in a gear shift motor for switching between a four wheel drive mode and a two wheel drive mode, when rotation of the motor has come to a stop due to an overload, rotational energy of the motor is accumulated in a torsion spring, and when the overload is removed this is released to drive the load quickly, and in the load-stop state the duty ratio is lowered so that an excessive lock current does not flow through the motor, and rotation of the motor is detected by a rotation sensor.
In Patent Document 2, ‘Safety Apparatus of Power Window’, technology is disclosed in which a potentio-sensor (variable resistance) for detecting the rotational position of a motor for driving the opening and closing of a window is provided, the detection output of the potentio-sensor at a fully open position is stored as a calibration value, and a safety control region in the vicinity of before fully closed is detected.
In Patent Document 3, ‘Engine Control Apparatus for Car’, the concept is disclosed of turning off a power supply relay with a delay after a power supply switch is turned off and in that delay time returning to an origin a stepping motor for controlling idling rotation of an engine.
In other art related to the present invention, Patent Document 4, ‘Breakdown Diagnosing Apparatus’, discloses technology for diagnosing a wire-break or short-circuit of a potentiometer and failure of a motor part in an apparatus wherein a motor actuator detects a potentiometer signal and uses it to control a stop position.
And in Patent Document 5, ‘Engine Control Apparatus’, relating to the present invention, detailed technology is disclosed relating to, in electronic throttle control for electrically controlling a throttle valve aperture, besides an initial position return mechanism of a throttle valve driving mechanism, failure determining means and good source determining means relating to an accelerator position sensor and a throttle position sensor installed as a double system.
Patent Document 1: JP-A-11-089268 (FIG. 1, Abstract)
Patent Document 2: JP-A-2000-274140 (FIG. 6, Abstract)
Patent Document 3: JP-A-05-018315 (FIG. 1, Abstract)
Patent Document 4: JP-A-2000-236685 (FIG. 1, Abstract)
Patent Document 5: JP-A-2003-161194 (FIG. 2, Paragraph 0037; FIG. 5, Paragraph 0047)
In the case of the ‘Actuator Control Apparatus’ of Patent Document 1, it is effective in an apparatus of a construction such that the efficiency of the motor drive system is poor and reverse-driving the motor from the load side is difficult, but if the efficiency of the drive system is high a holding current for preventing reverse-rotation becomes large, and there is a risk of driving transistors and the motor burning out.
And, when a forward limit position and a reverse limit position have not been detected correctly, there is a danger of unnecessary driving being carried out at the limit positions and of an abnormal state arising such that driving is impossible.
Whereas the apparatus of Patent Document 1 has a construction wherein the rotational position of the motor can be detected with a rotation sensor, in the ‘Safety Apparatus of Power Window’ of Patent Document 2 the rotational position is detected by an initially calibrated potentio-sensor, the motor has an ample torque such that it can drive the window immediately before fully closed and fully open, and in a safety management region where there is a danger of the window trapping something, if the motor slows down, disengaged drive is temporarily carried out and the motor is stopped.
Thus it is enough if the motor stops when an overload state arises at an intermediate position, and there is no mention of a method of escaping from an overload state.
In the case of the ‘Engine Control Apparatus for Car’ of Patent Document 3, means for initializing an actuator after a power supply switch is cut and the engine stops is disclosed, but there is no mention of a method of escaping from an overload state.
Similarly, Patent Document 4 and Patent Document 5 disclose methods for identifying trouble with a potentio-sensor (variable resistance) detecting the rotational position of a motor, and do not touch upon a method of escaping from an overload state.